In the production facilities of a semiconductor manufacturing system or the like, a substrate that is a work undergoes a plurality of kinds of processes. To do this, production facilities of this type must sequentially efficiently transport a work through a plurality of processing apparatuses.
For example, Japanese Patent Laid-Open No. 9-255114 discloses a conventional transport system in which a host computer unitarily manages transport paths and executes transport control of each transport unit. Japanese Patent Laid-Open No. 7-287729 discloses a system which adds a barcode to each object to be inspected as an object to be transported to identify it. A conveyor reads the barcode and selectively transports each object to be inspected to an inspection apparatus or another conveyor. Japanese Patent Laid-Open No. 2000-117594 discloses a system which adds an ID tag to each work and writes information about process control of the work in the ID tag at the start of the production line. Transport information about the type of each process the work should undergo is written in the ID tag. The work is transported through the processes via a path complying with the transport information.
In a system having only one transport path from a transport source to a transport destination, if the transport equipment is partially faulty, or the work transport delays in the transport path, the work transport is completely tied up, resulting in a large decrease in the work transport efficiency. This leads to a decrease in the operating ratio of, for example, a processing apparatus of the transport destination and a decrease in the production efficiency of the whole production facilities. This problem can be solved by forming a plurality of transport paths from the transport source to the transport destination and appropriately selecting one of them for each work.
However, when a plurality of transport paths are formed between a transport source and a transport destination in the system in which a host computer unitarily manages the transport path of each work, it is necessary to cause the host computer to designate the transport direction of a work at each branch point of the transport path. The load on the host computer becomes too heavy when simultaneously transporting many works.
On the other hand, in the system described in Japanese Patent Laid-Open No. 7-287729 or 2000-117594, which adds a barcode or ID tag to each work, and performs transport control of each work by reading information recorded in the barcode or ID tag, the load on the host computer can be lighter. However, the technique disclosed in Japanese Patent Laid-Open No. 7-287729 records the type of each work (object to be inspected) in a barcode and is usable only in a system which uniquely determines a transport path in accordance with the type of a work. The technique disclosed in Japanese Patent Laid-Open No. 2000-117594 records, in an ID tag, processes each work should undergo and is usable only in a system which uniquely determines a transport path to each process.